The invention relates to thermostats for regulating the flow of a fluid, in particular in a heat engine cooling circuit.
A thermostat as shown in FIGS. 1, 2 and 3 is known and is insertable between fluid pipes or preferably directly adaptable to the cylinder head of an engine.
This thermostat comprises a case 1 forming an elbow, usually of aluminum or molded aluminum alloy, adapted to be fixed to a support S (flange of a fluid pipe or cylinder head of an engine) and in which extends an inner passageway 2 for the fluid including a bend and having a fluid outlet region 21 remote from the support and a fluid inlet region 22 adjacent to the support, and a thermostatic element 3 disposed in the passageway and comprising two parts 31, 32 which are movable relative to each other.
A first part 31 of the thermostatic element 3 is maintained in a fixed position in the case. A second part 32 extends on the upstream side of the first part and carries a closing device 4 adapted to cooperate with a seat 23 provided in a narrowed region of the case. The second part is movable in translation relative to the first part for moving the closing device away from and toward the seat to a position of contact with the seat.
The free end of the first part 31 of the thermostatic element 3 is supported in a socket 10 centered on the longitudinal axis of the passageway, carried by at least one longitudinal rib extending radially in the passageway 2 from the wall of the latter; the second part 32 is carried and guided in its movement by a bridge 5 which is in contact by at least one region of its periphery with the wall of the passageway 2 and provided with a central opening in which this second part is slidably mounted. The closing device 4 and the bridge 5 are subjected to the force exerted by a coil spring 6, here cylindrical, which biases them away from each other.
The case 1 is in two parts 1A, 1B in which there are arranged respectively the fluid outlet region 21 and the fluid inlet region 22, and the thermostatic element is disposed in a portion of the fluid outlet part which extends along a rectilinear central axis, the upstream portion of the outlet part 1A being itself disposed in the downstream portion of the inlet part which is in the form of an elbow.
The upstream portion of the outlet part 1A comprises two fingers 11 which extend on the upstream side of the seat 23 the wall of the passageway for the fluid. The fingers 11 are diametrally opposed and define two respective transverse grooves in confronting relation; the bridge 5 is held fast against the upstream shoulders of these grooves 12 under the effect of the spring 6.
The two parts 1A, 1B constituting the case 1 comprise externally confronting flanges 13, 14 having ears provided with openings for the passage of fixing screws; the seal between the two parts 1A, 1B is provided by an elastically deformable annular sealing element 7 which is inserted in a groove extending circumferentially in one of the flanges in confronting relation to the other flange and is crushed against this other flange.
The outlet part 1A of the case further comprises a pipe 16 extending radially outside the outlet part and having its inner passage opening into the passageway on the downstream side of the seat 23; likewise, the inlet part 1B of the case further comprises an attached pipe 17 extending outwardly and having its inner passage opening into the passageway on the upstream side of the seat.
The case 1 is generally in the form of a right-angled elbow bearing in mind the implantation of the various components disposed under the hood of the vehicle engine, and the upstream portion of the outlet part 1A comprising the two fingers 11 between which the upstream region of the movable part 32 of the thermostatic element 3 is disposed extends in the downstream portion and in the elbow of the inlet part 1B.
The seal between the case 1 and its support is provided by an elastically yieldable sealing element 8 inserted in a recess extending around the inlet opening of the inlet region 22 of the inlet part 1B.
Consequently, the thermostat is made up of a relatively large number of parts and the thermostatic element 3 can only be mounted and dismounted through the upstream end of the outlet part 1A when the two parts 1A, 1B constituting the case 1 are separated; moreover, the force exerted by the bridge 5 biased by the spring 6 is exerted on the case 1 and more precisely on the upstream fingers 11 of the outlet part 1A which are relatively fragile, which jeopardizes the reliability of the case and consequently of the thermostat, unless there is used a relatively strong material such as relatively expensive aluminum or an aluminum alloy.